The DC-DC converter has a configuration in which a first full-bridge circuit and a second full-bridge circuit are connected via a transformer. A control circuit controls soft switching of each switching element. An inductor current flowing through the transformer or an equivalent inductor equivalent to the transformer at a time of switching of turning on or off each switching element is greater than or equal to a threshold current. When the first full-bridge circuit and the second full-bridge circuit have different output voltages V1 and V2, the control circuit causes the inductor current at start times t4 and t8 of a polarity inversion period to approach the inductor current at end times t5 and t9, the polarity inversion period being a period in which V1 and V2 have reverse polarities. This suppresses an increase in loss resulting from a flow of large current and enables ZVS control.
Legal claims defining the scope of protection, as filed with the USPTO.
1. A DC-DC converter comprising: a first full-bridge circuit including four switching elements that include a capacitor serving as a parasitic capacitance or an external parallel-connected capacitor; a second full-bridge circuit including four switching elements that include a capacitor serving as a parasitic capacitance or an external parallel-connected capacitor; a transformer including a first winding and a second winding, the first winding being connected to said first full-bridge circuit, and the second winding being connected to said second full-bridge circuit and magnetically coupled to said first winding; an inductance component connected in series with said first winding or said second winding; and a control circuit that controls soft switching of each switching element in each of said first full-bridge circuit and said second full-bridge circuit, wherein an inductor current flowing through an equivalent inductor at a time of switching of turning on or off each switching element is greater than or equal to a threshold current that is not zero, the equivalent inductor being equivalent to said transformer and said inductance component, and wherein when said first full-bridge circuit and said second full-bridge circuit have different output voltages, said control circuit controls a value of said inductor current at a start time of a polarity inversion period to approach a value of said inductor current at an end time of said polarity inversion period, the polarity inversion period being a period in which an output of said first full-bridge circuit and an output of said second full-bridge circuit have reverse polarities.
2. The DC-DC converter according to claim 1 , wherein said control circuit adjusts a voltage output period of said first full-bridge circuit in accordance with an input voltage of said first full-bridge circuit, and adjusts a voltage output period of said second full-bridge circuit in accordance with an input voltage of said second full-bridge circuit.
4. The DC-DC converter according to claim 1 , wherein said threshold current is set such that energy accumulated in said equivalent inductor becomes greater than or equal to energy accumulated in two of said capacitors.
Cooperative Patent Classification codes for this invention. Click any code to explore related patents in that topic.
April 24, 2019
May 31, 2022
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